Done this on my car 156kmiles done as I was getting a flashing battery light on the dash, read up some stuff and forum members were pointing at the Voltage regulator on the alternator. In the end I bought a new alternator at a cost of £154 with a £30 refund when I return my old unit.

Anyway I used the op to help me out taking the alternator out except for I didn't have to remove everything mentioned only the fan housing for better access and the air scoop and air filter, I then got easy access to the Alt. Took me no time at all about 30 mins in total. I also took the benefit of fitting new belts as the serpentine belt was cracked all the way round, so good job really.

Just to confirm on my model 2000 328CI I had the Torx 50 bolts in the tensioners as some have mentioned an Allen head bolt in there..also the serpentine belt tensioner was stiffer than the AC one so watch the Torx Head socket doesn't come out as you could easily damage the radiator matrix, so take your time on that one..The AC tensioner was easy..

Thanks for OP for starting this thread..the E46 forum comes to assistance again..thanks.